A Freeze-drying Formulation and Target Specificity of Double-stranded RNA-expressing Bacteria to Control Insect Pests
2016
Kim, E., Andong National University, Andong, Republic of Korea | Kim, Y., Andong National University, Andong, Republic of Korea
Double-stranded RNA (dsRNA) has been applied to control insect pests by its suppressive activity against specific target genes. Integrin is a heterodimer (alpha and beta) transmembrane protein and plays a critical role in cell-to-cell or cell-to-extracellular matrix interactions in eukaryotes. Suppression of beta subunit integrin gene expression by its specific dsRNA (= dsINT) induces significant mortality against target insects. Furthermore, a recombinant bacterium expressing dsINT is potent to kill target insects. However, it is necessary to develop a formulation technique of the dsRNA-expressing bacteria to apply the bacterial insecticide against field populations. This study formulated the recombinant bacteria by freeze-drying and tested its control efficacy against target insects. The formulation maintained significant insecticidal activity against last instar larvae of Spodoptera exigua. While a commercial Bacillus thuringiensis (Bt) insecticide exhibited only about 60% insecticidal activity against S. exigua last instar, an addition of the dsINTexpressing bacterial formulation significantly enhanced the Bt insecticidal activity. The dsINT-expressing bacterial formulation exhibited relative selectivity to target insects depending on sequence similarity. These results indicate that a freeze-dried form of dsRNA-expressing bacteria keeps its insecticidal activity.
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